Eating and drinking while driving almost doubles the risk of a car crash although three-quarters of motorists do so, according to British research.

Eating at the wheel 'doubles crash risk'

Eating and drinking while driving almost doubles the risk of a car crash although three-quarters of motorists do so, according to British research.

Using a driving simulator, the study found motorists misjudge the risks caused by eating and drinking while behind the wheel and, although they try to compensate by driving more slowly, they are often unable to brake in time to avoid a crash.

"The results of our experiment strongly indicate that eating or drinking while driving increases the risk of a crash," Dr Mark Young from Brunel University said.

"Drivers may not perceive the risk to be any higher than other menial in-car tasks, but the impaired reactions combined with the increased workload suggest drivers should exert caution," he said in a statement.

During the study, participants drove an urban route once without eating and then again while eating from a bag of sweets or drinking from a bottle of water.

The number of crashes doubled during the food and drink trial with nine in 10 occurring at the point the driver was eating sweets or sipping water.

Although in the UK it is illegal to use hand-held mobile phones while driving, as in Australia, there are no specific laws about eating or drinking, although motorists can run the risk of being charged with other offences.

One well publicised case last year involved a motorist being fined STG60 ($A148) for eating an apple.